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June 20, 2013

APTRANSCO SUB ENGINEERS 2012 Previous Paper Electrical

The speed torque characteristics of a series
motor is a/an--------------(Hyperbola)

In ad dc
generator,
if the variable loss is equal to constant loss, then efficiency
is-------(Max)

The armature of a dc machine is laminated to
reduce-----(eddy current loss)

The initial flux in a dc generator is provided by-----(residual magnetism)

For the operation of milling machine, which
motor is used----( DC shunt motor)

In a series motor, the torque is----(
proportional to square of armature current)

By conducting swinburn’s test on a dc machine,
the following losses can be determined-----( constant losses)

The series motors have relatively----( High
starting torque)

In a dc shunt motor, the torque developed is
15Nm at 10A of load current. If the load current is doubled, the new
torque will be----(30Nm).

The internal characteristics of s dc
shunt generator is a plot between----(Eg and Ia)

The back emf of motor at the time
starting is -----------(zero)

At low flux densities, the flux in a dc generator varies----(Linearly with field current)

Three resistances of R ohms each are connected in delta. Its equivalent resistances in star
connection per phase is -----(R/3 each)

The RMS value of a triangular wave of
alternating quantity having peak value 3A is -----(sqrt 3)

In as series RL circuit, the voltage across
the resistance is 40V and voltage across inductance is 40v. Then the total
voltage across the series circuit--------(56.56V)

A transformer can have regulation closer
to zero---( on leading pf)

The full load copper loss of a
transformer is 1600watts. At half load, the copper loss----(400watts)

A 440/110, 1- phase transformer has a
primary resistance of 0.03ohms and secondary resistance of 0.02ohms. its
iron losses at normal input are 150 watts. The secondary current at which
the maximum efficiency will occur is -------(82.80A)

Which of the following transformers
should never have the secondary open circuited while primary is
energized---------(CT)

An isolation transformer has primary to
secondary turn’s ratio of-------(1:1)

In a 50 KVA, 1-phase transformer, the iron
loss is 500W and full load copper loss is 800W. The efficiency of the transformer at full load
at 0.8 pf lagging is----(96.85%)

A synchronous motor can be used as a synchronous
capacitor when it is---(over excited)

The harmonic component of the generated emf
will be more in alternators with-------(Full pitch coils)

V-curves for a synchronous motor represent the
relation between---(Ia and If)

The crawling in an induction motor is caused
by-----(harmonics developed in the motor)

The ratio of starting torque to normal torque
in case of a star delta starter will be---(1/3)

A 3-phase, 440v, 50hz induction motor has 4%
slip. The frequency of rotor emf will be----(2Hz)

In a tuned line-----------( receiving end
voltage and current are numerically equal to corresponding sending end
values)

The max torque in an induction motor depends
on------(frequency)

which of the following motors will have
relatively high power factor---(capacitor run motor)

which of the following motors can be used for
unity pf---(Schrage motor)

which of the following turbines will be used
for heads from 500m to 200m--------(Francis)

The sudden change of pressure in penstock
pipes due to sudden reaction of load is avoided using-------(surge tank)

Which of the following heat exchangers is used
to raise the temperature of steam from normal to super saturation
level------(superheater)

which of the following treatments for water is
used to remove non carbonate hardness-----(Soda treatment)

The hoppers in electrostatic precipitator are
generally----------in shape(pyramidal)

The purpose of cooling
tower is---(
to cool the steam in the condenser)

which is used to reduce the speed of the neutrons
in a nuclear reactor-----(moderator)

which of the following is a cladding material
in nuclear reactor---(Magnesium)

In which of the following reactors, reactor
control is achieved by varying moderator level ----------(CANDU)

A generating station has a connected load of 450MW and a maximum demand of 250MW.
The units generated are 615*10^6 per annum. The load factor of the station
is -----(0.281)

The plant capacity is determined
by-------(Plant use factor)

A power plant has a maximum demand of 15MW.
The load factor is 50% and the plant factor is 40%. The operating reserve
is ----(3.75MW)

A transformer is rated at 66Kv/4001V, 1000KVA,
5% reactance. The short circuit MVA of the transformer when connected to infinite bus is-----(20MVA)

The power frequency rms voltage, that appears
across the breaker contacts after the transient oscillations die out and
final extinction of arc that results in all the poles is
called-------(recovery voltage)

In resistance switching, the function of shunt
resistor----------(reduces the rate of rise of restriking voltage)

The no. of poles per phase of breaker is a
function of------(Operating voltage)

The capacitor switching is easily done
with------(vacuum CB)

A distance relay is inherently directional if
its characteristics on R-X diagram is------( a circle that passes through
origin)

The most efficient torque producing actuating
structure in an induction relay is ---------(induction cup structure)

The line trap unit employed in carrier current
relaying----(offers high impedance to carrier frequency signals)

The protection relay used for low fault
settings and high operating speeds in a transformer is
-----------(Harmonic restraint relay)

The wattmetric relay with directional
characteristic is used for protection of generator against------(failure
of prime mover)

The
best suited
relay for 3- zone protection scheme is ----(Mho relay)

The rule 77 of Indian electricity rules(1956)
for over head lines gives information about----(clearance above ground of
lowest conductor)

The stringing charts are used to
calculate-----(Tension and sag at any temperature)

Due to proximity effect, the effective
internal reactance of the conductor---(decrease)

The inductance of a single phase two wire
transmission line per kilometer gets doubled when
the----------------(distance between the wires is increased as square of
the original distance)

a transmission line of 210km length has
certain values for A,B,C and D parameters. If the length of line is made
100km then------(A increases and B decreases)

The surge impedance loading of the line is
proportional to—(V^2)

Under no load conditions the current in a
transmission line is due to------( capacitance of the line)

For a transmission line, the no load receiving
end voltage is more than the sending end voltage. This is
called---------(Ferranti effect)

Corona loss can be reduced by the use of hollow
conductor, because-----( for a given cross section, the radius of the
conductor is increased)

The non shielding method of over voltage
protection is
based on the principle of --------(insulation breakdown)

The valve elements of non linear resistance in
valve type lighting arrester are made up of -----------(silicon carbide)

Which of the following lightning arresters, can discharge currents, between 65000 to
100000A-------(line type)

Which of the following is used to reduce tower
footing resistance-------(ground rods)

In substations, the breaker maintenance facility is provided in the----(main and transfer bus
scheme)

In case of rigid bus arrangement, the size of
aluminum pipe used for voltage level of 66KV----------------(65mm)

For low
voltage applications
up to 11KV, which of the following insulators is preferred-------(pin type)

In a 5 insulator disc, string capacitance
between each unit and earth is 1/6 th of the mutual capacitance. The
voltage distribution across the middle unit as % of voltage applied
is------(17.1)

An electric train taking of constant current
of 600A moves on a section of line between two substations 8km apart
maintained at 575V and 590V resp. The track resistance is 0.04ohm per km
both go and return. The point minimum potential along the track is at a
distance from 575V substation is----(3.67Km)

which of the following is the most economical
ac distribution system------( ac 3 phase 3 wire)

for a distributor design, if the voltage
rating is increased by ‘n’ times, the conductor size reduces to ----of the
original(1/n2)

The pointer of an indicating instrument is
generally made of ------------(aluminum)

Electrostatic instruments are used
as-------------only(voltmeters)

In a dynamometer wattmeter, the moving coil is
the----(potential coil)

A 50V range voltmeter has a sensitivity of 20
k-ohms/volt. The total resistance of the voltmeter is -----(1MOHM)

An RLC series resonant circuit has a Q of 15
and a source voltage of 50V. the voltage across the capacitor at resonance
is -----(750V)

At parallel resonance conditions the power
factor is--------(unity)

In AC circuit, V and I are given by:
V=100sin(100t) V and I=100sin(100t+∏/3)mA. The power dissipated in the
circuit is------(2.5W)

In the measurement of 3-phase power by two
wattmeter method, the two wattmeter’s indicate equal readings if the power
factor is----(unity)